问题 解答题

近视眼的同学所戴的近视眼镜属于凸透镜.______.

答案

看近处物体时,必须通过睫状肌的收缩作用,使晶体的凸度增加,使近处的物体像能够落在视网膜上,才能看的清楚.长时间的近距离作业,如读书、写字、看电视、玩游戏机等,使眼睛长时间的调节紧张,头部前倾,眼球内不断的充血,眼内压相应的增高,以及眼外肌的紧张和压迫眼球,或者因调节时牵引涡状静脉,妨碍了血液的流通,使巩膜的抵抗力减弱,导致晶状体过度变凸,不能恢复成原状;严重时使眼球的前后径过长,使远处物体反射来的光线形成的物像,落在视网膜的前方,因此不能看清远处的物体.形成近视.需要佩戴凹透镜进行矫正;远视眼是由于眼轴较短,或者晶状体的曲度过小,在不使用调节状态时,平行光线通过眼的屈折后主焦点落于视网膜之后.而在视网膜上不能形成清晰的图象.需要佩戴凸透镜进行矫正.

故答案为:×

单项选择题
阅读理解

阅读理解。

     Dr. Sylvia Earle wants you to stop eating fish. It's not because fish are endangered,though wild

fish stocks in many oceans are very low. It's not because they're bad for you, though fishin many

areas are exposed to poisonous substances in the water. It's because they're smart.

     "Fish are sensitive, they have personalities',says the marine biologist. For Earle, eating afish would

be like eating a dog or a cat. "I would never eat anyone I know personally."

     There's a lot more to fish than meets the eye: they talk to each other, they like to betouched, and

they engage in behavior that can seem very human. They can remember thingsand learn from experience.

Earle and a growing number of animal rights activists see these asstrong arguments against eating fish

altogether.

     The activists also point out that fish feel pain and fish suffer horribly on their way from the sea to

the supermarket. "While it may seem obvious that fish are able to feel pain, likeevery other animal,

some people think of fish as swimming vegetables," says Dr. Lynne Sneddon. "Really,it's kind of a

moral question. Is the enjoyment you get from fishing (oreating fish) more important than the pain of

the fish?"

      Fishermen and (fried) fish lovers are doubtful. "I've never seen a smart fish," says Marie Swaringen

as she finishes off a plate of fish at a Seattle seafood restaurant. "If they were verysmart, they wouldn't

get caught. "

     "For years, everyone's been telling us to eat fish because it's so good for us," says another diner.

''Now I've got to feel guilty while I'm eating my fish? What are they going to think of next? Don't eat

salad because cucumbers have feelings?"

1. Dr. Sylvia Earle discourage people from eating fish because.

A. there are not that many wild fish in the ocean

B. fish actually are sensitive and have personalities

C. some ocean fish contain poisonous substances

D. fish are like dogs or cats that people know personally

2. We can infer from the passage that      .

A. all people don't agree with the idea to stop eating fish

B. people will be persuaded not to eat fish in the future

C. stopping eating fish will lead to people's not eating vegetables

D. we shouldn't care too much about the feeling of fish

3. By saying "There's a lot more to fish than meets the eye, " the writer means.

A. there are far more fish than other animals in the world

B. there are more fish in the world than people can see

C. people can see more fish if they pay more attention

D. fish are not that simple as they appear to people's eyes

4. What is the writer's attitude towards people eating fish?

A. Neutral.

B. Indifferent.

C. Approving.

D. Opposed.